Method for depositing nanolaminate thin films on sensitive surfaces

ABSTRACT

The present method provides tools for growing conformal metal nitride, metal carbide and metal thin films, and nanolaminate structures incorporating these films, from aggressive chemicals. The amount of corrosive chemical compounds, such as hydrogen halides, is reduced during the deposition of transition metal, transition metal carbide and transition metal nitride thin films on various surfaces, such as metals and oxides. Getter compounds protect surface sensitive to hydrogen halides and ammonium halides, such as aluminum, copper, silicon oxide and the layers being deposited, against corrosion. Nanolaminate structures ( 20 ) incorporating metal nitrides, such as titanium nitride ( 30 ) and tungsten nitride ( 40 ), and metal carbides, and methods for forming the same, are also disclosed.

FIELD OF THE INVENTION

The present invention relates generally to depositing thin films onsubstrates by alternated self-saturating chemistries. More particularly,the present invention relates to preventing the corrosion of materialsin a substrate while employing corrosive species during the formation ofthin films.

BACKGROUND OF THE INVENTION

Atomic Layer Deposition (ALD), originally known as Atomic Layer Epitaxy(ALE), is an advanced variation of CVD. ALD processes are based onsequential self-saturated surface reactions. Examples of these processesare described in detail in U.S. Pat. Nos. 4,058,430 and 5,711,811. Thedescribed deposition processes benefit from the usage of inert carrierand purging gases, which make the system fast. Due to theself-saturating nature of the process, ALD enables almost perfectlyconformal deposition of films on an atomically thin level.

The technology was initially developed for conformal coating ofsubstrates for flat panel electroluminescent displays that desirablyexhibited high surface area. More recently, ALD has found application inthe fabrication of integrated circuits. The extraordinary conformalityand control made possible by the technology lends itself well to theincreasingly scaled-down dimensions demanded of state-of-the-artsemiconductor processing.

While ALD has many potential applications to semiconductor fabrication,integrating these new processes into established process flows canintroduce many new issues. Accordingly, a need exists for improved ALDprocesses.

SUMMARY OF THE INVENTION

In accordance with one aspect of the invention, a method is provided forforming a nanolaminate structure on a substrate within a reaction spaceby an atomic layer deposition (ALD) type process. The nanolaminatestructure has at least two adjacent thin film layers, including at leastone metal compound layer. Each thin film layer is in a different phasefrom adjacent thin film layers.

In accordance with another aspect of the invention, a nanolaminatestructure is provide with at least three thin film layers. Each layerhas a thickness less than about 10 nm. At least one of the layersselected from the group consisting of metal carbides and metal nitrides.

In accordance with another aspect of the invention, a method is providedfor depositing a material on a substrate in a reaction space. Thesubstrate has a surface susceptible to halide attack. The methodincludes providing alternated pulses of reactants in a plurality ofdeposition cycles, where each cycle includes:

-   -   supplying a first reactant to chemisorb no more than about one        monolayer of a halide-terminated species over the surface;    -   removing excess first reactant and reaction by-product from the        reaction space; and    -   gettering halides from the monolayer prior to repeating the        cycle

BRIEF DESCRIPTION OF THE DRAWINGS

These and other aspects of the invention will be readily apparent to theskilled artisan in view of the description below and the appendeddrawings, which are meant to illustrate and not to limit the invention,and in which:

FIG. 1 is a Scanning Electron Micrograph (SEM) taken from a copper filmformed by physical vapor deposited (PVD). The measurement voltage was 10kV.

FIG. 2 is an SEM taken from a PVD copper covered with TIN in accordancewith an ALD process that did not employ a getter or scavenger pulse. Theblack areas of the picture indicate areas of the copper etched duringthe TiN processing.

FIG. 3 is as SEM taken from a PVD copper covered first with WN and thenwith TiN in accordance with a preferred embodiment of the presentinvention (Example 6).

FIG. 4 is an SEM taken from an electrochemically deposited (ECD) coppercovered first with WN and then with TiN, in accordance with a preferredembodiment of the present invention (Example 6).

FIG. 5 is a graph depicting the equilibrium state of compounds betweentantalum, fluorine and copper as a function of temperature. The sourcechemicals for the calculations were 10 mol TaF₅ and 1 mol Cu.

FIG. 6 is a schematic cross-section of an exemplary workpiece over whichmetal or metal compound deposition is desired, consisting of a dualdamascene structure in a partially fabricated integrated circuit, havingcopper and insulating oxide surfaces exposed.

FIG. 7 illustrates the workpiece of FIG. 6 after lining the dualdamascene trench and contact via with a conformal thin film inaccordance with the preferred embodiments.

FIG. 8 is a flow chart generally illustrating a method of forming abinary compound by Atomic Layer Deposition (ALD), in accordance withseveral of the preferred embodiments.

FIG. 9 is a schematic diagram of the first four thin film layers of anALD nitride nanolaminate and the pulsing sequence for each thin filmlayer.

FIG. 10 is a transmission electron microscopy (TEM) picture of a nitridenanolaminate structure.

FIG. 11 is a table showing refractive metal halides that react (X) or donot react (O) with copper metal. (X) designates a lack of sufficientdata for drawing conclusions regarding the ability to employ thesereactants without gettering. The metals are in their highest possibleoxidation state. Gibb's free energies of the reactions were calculatedby a computer program (HSC Chemistry, version 3.02, Outokumpu ResearchOy, Pori, Finland).

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present disclosure teaches methods for protecting sensitive surfacesduring ALD deposition. The skilled artisan will appreciate that, whileapplicable to nanolaminate construction, the protection of sensitivesurfaces from corrosion has application in other contexts, and viceversa

Definitions

For the purpose of the present description, an “ALD process” designatesa process in which deposition of material onto a surface is based onsequential and alternating self-saturating surface reactions. Thegeneral principles of ALD are disclosed, e.g., in U.S. Pat. Nos.4,058,430 and 5,711,811, the disclosures of which are incorporatedherein by reference.

“Reaction space” is used to designate a reactor or reaction chamber, oran arbitrarily defined volume therein, in which conditions can beadjusted to effect thin film growth by ALD.

“Adsorption” is used to designate an attachment of atoms or molecules ona surface.

“Surface” is used to designate a boundary between the reaction space anda feature of a substrate.

“Getter,” “gettering agent” or “scavenger” is used to designate avolatile species that can form new volatile compounds from halogen orhalide species adsorbed on the surface, or from halides in the reactionspace (e.g., hydrogen halides or ammonium halides). Typically, the newhalogen compounds are less corrosive to exposed features of theworkpiece than are hydrogen halides or ammonium halides.

The symbols “—” and “═” attached with one end to an atom designate thenumber of bonds to unspecified atoms or ions.

A subscript “x” in metal nitrides (e.g., WN_(x) or TiN_(x)) is used todesignate the transition metal nitrides that are not necessarilystoichiometric, having a wide range of phases with varyingmetal/nitrogen ratios.

A subscript “x” in metal carbides (e.g., WC_(x) or TiN_(x)) is used todesignate the transition metal carbides that are not necessarilystoichiometric, having a wide range of phases with varying metal/carbonratios.

“Nanolaminate structure” means a layered structure comprising stackedthin film layers of different phases with respect to the growthdirection of the nanolaminate. “Alternating” or “stacked” means that theadjacent thin film layers differ from each other. In a nanolaminatestructure there are always at least two phases of molecules. Preferably,at least three adjacent phases are present. A single phase exists wherethe molecules or atoms in a space are so evenly mixed that nodifferences can be found between different parts of the space byanalytical methods. Different phases can be due to any differencesrecognized in the art, for example different crystal structures,crystallite lattice parameters, crystallization stage, electricalconductivity and/or chemical composition of the thin film on either sideof the phase interface.

Desirably, each phase or layer in the stack is thin, preferably lessthan about 20 nm in thickness, more preferably less than about 10 nm andmost preferably less than about 5 nm each. “Thin film” means a film thatis grown from elements or compounds that are transported as separateions, atoms or molecules via vacuum, gaseous phase or liquid phase fromthe source to the substrate. The thickness of the film depends upon theapplication and may vary in a wide range, preferably from one atomiclayer to 1,000 nm.

“Metal thin film” designates a thin film that consists essentially ofmetal. Depending on the reducing agent the metal thin film may containsome metal carbide and/or metal boride in an amount that does not have anegative effect on the characteristic metal properties of the film, orthe characteristic properties of a nanolaminate.

Integration Issues

Halides generally, and particularly transition metal halides, areattractive source chemicals for ALD due to their high volatility anddurability against thermal decomposition. Of these halides, compoundsthat are liquids or gases near room temperature, such as TiC₄ and WF₆,are preferred because they do not generate solid particles at the sourcecontainer. In addition to their volatility, many such halide compoundsare particularly useful for ALD processing because they allowchemisorption of a species of interest (e.g., a metal-containingspecies), leaving no more than a monolayer of the species terminatedwith halide tails. The halide tails prevent further chemisorption orreaction of the species of interest, such that the process isself-saturating and self-limiting.

Metal halides can be employed, for example, in the formation of metal,metal nitride and metal carbide thin films by ALD processes. However,these processes have not resulted in the perfectly conformal depositiondesired of ALD. FIG. 2 and the discussion of Examples 1, 2 and 4demonstrate, for example, corrosive damage sustained by “exposed” copperduring ALD formation of metal nitrides and carbides using metal halidesalternated with ammonia In fact, Example 4 demonstrates that such damagecan be sustained even when the copper was covered by 5 nm of tungstenmetal.

ALD processes using metal halides and source chemicals with highhydrogen content, can release hydrogen halides (e.g., HF, HCl) asreaction by-products. These reactive by-products can destroy certainmetal surfaces, leaving deep pits in the metal or even removing all themetal. Silicon dioxide is also prone to corrosion due to the formationof volatile silicon halides. These hydrogen halides can also combinewith other reactants during an ALD phase, such as with excess NH₃ duringa nitrogen phase, to form additional harmful species, such as ammoniumhalides (e.g., NH₄F) that exacerbate the corrosion problem. Thus,by-products from alternating halide- and hydrogen-bearing reactants tendto corrode exposed materials of a partially fabricated integratedcircuit, like aluminum, copper and silicon dioxide.

Preferred Workpiece

The preferred embodiments involve deposition of metal, metal carbide andmetal nitride thin films by ALD upon the surface of a substrate. In oneembodiment the thin films form nanolaminates. More particularly, theembodiments involve deposition upon “sensitive” surfaces that aresusceptible to corrosion in the presence of halides and especiallyhydrogen halides. Such sensitive surfaces include, for example, metalssuch as aluminum and copper, as well as silicon compounds such assilicon oxide and silicon nitride.

As set forth in more detail below, such sensitive surfaces are generallycharacterized as having negative or near zero Gibb's free energy(ΔG_(r)) for reactions between the surfaces and hydrogen halides orammonium halides.

FIG. 6 illustrates a dual damascene context in which deposition isdesired over a plurality of such materials simultaneously. The structureincludes a first or lower insulating layer 50, a form of silicon oxide,particularly deposited by plasma enhanced CVD (PECVD) employingtetraethylorthosilicate (TEOS) as a precursor. The insulating layer 50is formed over a barrier layer 51 (typically silicon nitride), which inturn overlies a conductive element 52. The conductive element 52 in adual damascene context typically comprises a highly conductive wiringmetal and most preferably comprises copper. Over the first insulatinglayer 50 is an etch stop 54 formed of a material with a significantlydifferent etch rate compared to the underlying insulator 50. The etchstop layer 54 (typically silicon nitride) includes a plurality ofopenings 55 across the workpiece to serve as hard mask in definingcontact vias. A second or upper insulating layer 56 (also PECVD TEOS) isformed over the etch stop 54, and a polishing shield 58 to stop a laterchemical mechanical planarizing (CMP) step. The polishing shield 58typically comprises a relatively hard material, such as silicon nitrideor silicon oxynitride.

As will be appreciated by the skilled artisan, the dual damascenestructure is formed by photolithography and etch steps to define aplurality of trenches 60 with contact vias 62 extending from the trenchfloors at discrete locations. The trenches 60 serve to define wiringpatterns for interconnection of electrical devices according to anintegrated circuit design. The contact vias 62 define locations whereelectrical connection to lower electrical elements or wiring layers aredesired in accordance with the circuit design.

The skilled artisan will appreciate that various alternative materialsand structures can be employed to accomplish these ends. For example,while the preferred insulating layers 50, 56 comprise PECVD TEOS, inother arrangements the material of these layers can comprise any of anumber of other suitable dielectric materials. For example, dielectricmaterials have recently been developed that exhibit low permittivity(low k), as compared to conventional oxides. These low k dielectricmaterials include polymeric materials, porous materials andfluorine-doped oxides. Similarly, the barrier 51, etch stop 54 andshield 58 can comprise any of a number of other materials suitable totheir prescribed function. Moreover, any or all of the layers 51, 54 and58 can be omitted in other schemes for producing dual damascenestructures.

As shown in FIG. 7, the dual damascene trenches 60 and vias 62 are thenlined with a thin film 150. The thin film 150 can be formed selectivelyover particular desired surfaces of the structure, but is mostpreferably formed in a blanket, conformal deposition by ALD, inaccordance with the preferred embodiments. In the illustratedembodiment, the thin film is conductive, allowing electrical signals toflow therethrough.

Integrated circuits contain interconnects that are usually made ofaluminum. Recently, copper has become an attractive material in thefield. Copper is, however, prone to diffusion to surrounding materials.Diffusion affects the electrical properties of the circuits and maycause active components to malfunction. Diffusion may be prevented by anelectrically conductive diffusion barrier layer. Amorphous films arebelieved to enhance the properties of diffusion barriers because the iondiffusion favors the grain boundaries of the thin films. Favoreddiffusion barriers are transition metal nitrides, such as TiN_(x),TaN_(x), and WN_(x). The inventors have also found metal carbides (e.g.,WC_(x)) to be good, conductive diffusion barriers.

Conventionally, a thin lining film in a dual damascene structureincludes a conductive adhesion sub-layer (e.g., tungsten metal), abarrier sub-layer (e.g., titanium nitride) and a seed sub-layer (e.g.,PVD copper). The preferred thin film 150 can comprise one or more ofthese sub-layers, formed by ALD, and can also comprise one or moresub-layers formed by other methods. The preferred embodiments, forexample, include a method of forming tungsten metal by ALD over oxideand copper structures without etching. However, it is generallydesirable to minimize the thickness of lining layers, to therebymaximize the volume of the structure occupied by a later-depositedhighly conductive metal (preferably copper). To this end, the preferredembodiments also provide means for depositing barrier layers directlyover both oxide and copper surfaces (or other sensitive surfaces)without etching the sensitive surfaces, or depositing barrier layersover extremely thin adhesion layers without corrosion.

As will be appreciated by the skilled artisan, following formation ofthe thin film 150, the trench 60 and via 62 can be filled with a highlyconductive material, such as electroplated copper. A polishing step thenensures individual lines are isolated within the trenches 60.

Nanolaminate Structures

Nanolaminates are layered structures that have enhanced diffusionbarrier properties. A nanolaminate consists of multiple thin film and isconstructed so as to create very complicated diffusion paths forimpurities through disruption of normal crystal growth duringdeposition. Thus, nanolaminates comprise alternating thin film layers ofdifferent phases, for example with different crystallite structures anddifferent crystallite lattice parameters.

According to a preferred embodiment of the invention, nanolaminatestructures are formed on the substrate. The nanolaminate structurespreferably are comprised of at least one transition metal compound thinfilm layer, desirably conductive and serving a diffusion barrierfunction. The metal compound can be a metal nitride or a metal carbide.The nanolaminate structures may also comprise one or more elementalmetal thin film layers.

The nanolaminate structures are preferably layered structures,comprising alternating, stacked thin film layers of materials withdifferent phases with respect to the growth direction of thenanolaminate. The nanolaminate structures preferably comprise materialswith at least two different phases. Thus, at least two adjacent thinfilm layers preferably have a different phase. For example they may havea structure, composition or electrical resistivity different from eachother. In a nanolaminate with three layers, at least one of the layerswill preferably have a phase different from the other two layers.

The nanolaminate structures preferably comprise at least two thin filmlayers. More preferably they comprise at least three thin film layers.When the nanolaminate structure comprises three film layers, it ispreferably a “sandwich” structure wherein the middle layer has adifferent phase from the outer two layers.

Preferably, the nanolaminates are grown such that the phase alternateswith the layers. Thus, every other layer preferably is of the samephase. However, all of the thin films of one nanolaminate structure canbe of different phases, for example if each thin film layer is made ofdifferent materials. This structure has a number of phase interfacesthat may impair the diffusion of ions in the structure.

An example of a nanolaminate structure is presented in FIG. 9, which isa schematic diagram of the first four thin film layers of a metalnitride nanolaminate produced by the ALD type process of the presentinvention. The pulsing sequence for obtaining each layer is indicated inFIG. 9. The layers are not to scale in the figure and the subscripts x,y, a and b are integers.

FIG. 10 illustrates the uniform growth and sharp interfaces betweenlayers in the preferred nanolaminates. FIG. 10 is a transmissionelectron microscopy (TEM) picture of a nitride nanolaminate structureshowing clearly separated 1.8 nm thin film layers of titanium nitride 30(light grey) and 4.5 nm thin film layers of tungsten nitride 40 (darkgrey).

The number of layers stacked in a nanolaminate structure may vary, butcan vary from 2 to 500, preferably from 3 to 300, more preferably from 4to 250 and even more preferably from 4 to 20. The thickness of ananolaminate structure is preferably from 2 molecular layers to 1,000nm, more preferably from 5 nm to 200 nm and even more preferably from 10nm to 100 nm. Desirably, each layer is thin, preferably less than 20 nmin thickness, more preferably less than about 10 nm, and most preferablyless than about 5 nm each.

The thin film layers that make up the nanolaminate structures of thepresent invention preferably have different phases or properties fromeach adjacent layer. These differences may be in the followingproperties, but one skilled in the art will recognize that otherproperties are contemplated and that the properties will vary dependingupon the types of thin films in the nanolaminate structure:

1. Crystallite structure. The crystallite structure varies according tothe deposited species, as well as according to the metal/nitrogen ratioof nitride thin film layers. The variation in crystallite structure canoccur in a number of details, including the space group, unit celldimensions and orientation of the crystallites on the thin film layer.

There are 230 space groups, such as face centered, cubic and hexagonal.Thus, a nanolaminate structure can be made by depositing on a substratealternating thin film layers having hexagonal and cubic space groups ofthe crystallite, respectively. Variation in the space group can changethe unit cell dimensions.

Unit cell is the smallest repeated atomic arrangement inside thecrystallite, and the size of a unit cell can vary. As an example, ananolaminate can be made by depositing alternating thin film layerscomprising materials with a small unit cell and a big unit cell.

The orientation of the crystallites on the thin film layer according tothe Miller indices may also vary. For example, a nanolaminate may havethe following structure: (100)/(111)/(100)/(111)/ . . . .

2. Composition. Composition refers to atomic make-up, such as themetal/nitrogen ratio in the illustrated nanolaminates that include metalnitride, or the metal/carbon ratio in the illustrated nanolaminates thatinclude metal carbide. An example of a nanolaminate structure comprisingdifferent phases due to the metal/nitrogen ratio is the following:Ta₃N₅/TaN/Ta₃N₅/TaN/ . . . . Another example is a structure wherein somethin film layers contain nitrogen and others do not, such as W/WN/W/WN/. . . .

3. Electrical Resistivity. Electrical resistivity also varies accordingto the metal/nitrogen ratio. Amorphous or near-amorphous structures mayhave clearly different resistivities when compared to each other. Ingeneral the more nitrogen is present in a thin film layer, the higherthe resistivity. An example of a possible nanolaminate structure is onecomprising alternating thin film layers of materials with lowresistivity and very low resistivity.

The nanolaminates of the present invention can be used, for example, asdiffusion barriers in integrated circuits. They can also be used as areflector for x-rays. The nanolaminate structure suitable for such anapplication preferably comprises thin film layers consisting of highatomic number transition metals or high atomic number transition metalnitrides and low atomic number elements or nitrides. In the context ofthe present invention the atomic number is considered to be “high” if itis at least approximately 15 or greater and “low” if it is approximately14 or less. The high atomic number nitrides are preferably preparedusing a source material comprising tungsten or tantalum. The low atomicnumber nitrides are preferably inorganic nitrides, particularlyberyllium, boron, magnesium, aluminum and silicon nitrides. Preferablythe thin film layers are arranged in the nanolaminate such that layerscomprising a high atomic number nitride are alternated with layerscomprising a low atomic number nitride.

The nanolaminate structures described herein, including metal nitride orcarbide on other conductive barrier layers, are particularly suitablefor interconnect barriers, as described with respect to FIG. 7.Moreover, these materials are sensitive to attack from hydrogen halidesand ammonium halides in the process of deposition. Accordingly, themethods of deposition described below enable quality nanolaminatestructures.

Preferred ALD Methods

The methods presented herein allow deposition of conformal thin filmsand nanolaminates from aggressive chemicals on chemically sensitivesurfaces. Geometrically challenging applications are possible due to theuse of self-limited surface reactions.

According to the preferred embodiments, thin films, particularlynanolaminate structures, are formed by an Atomic Layer Deposition (ALD)type process on integrated circuit workpieces or substrates that includesurfaces susceptible to halide attack. Such sensitive surfaces can takea variety of forms. Examples include silicon, silicon oxide (SiO₂),coated silicon, low-k materials, metals such as copper and aluminum,metal alloys, metal oxides and various nitrides, such as transitionmetal nitrides and silicon nitride or a combination of said materials.As noted above with respect to FIGS. 6 and 7, the preferred damasceneand dual damascene contexts include silicon oxide based insulators andexposed copper lines at the bottom of contact vias.

A substrate or workpiece placed in a reaction chamber is subjected toalternately repeated surface reactions of source chemicals for thepurpose of growing a thin film. In particular, thin films are formed bya periodic process in which each cycle deposits, reacts or adsorbs alayer upon the workpiece in a self-limiting manner. Preferably, eachcycle comprises at least two distinct phases, wherein each phase is asaturative reaction with a self-limiting effect. Reactants are thusselected such that, under the preferred conditions, the amount ofreactants that can be bound to the surface is determined by the numberof available sites and incidentally by the physical size of chemisorbedspecies (including ligands). The layer left by a pulse isself-terminated with a surface that is non-reactive with the remainingchemistry of that pulse. This phenomenon is referred to herein as“self-saturation”.

Maximum step coverage on the workpiece surface is obtained when no morethan about a single molecular layer of source chemical molecules ischemisorbed in each pulse. Each subsequent pulse reacts with the surfaceleft by the preceding pulse in a similarly self-limiting orself-terminating manner. The pulsing sequence is repeated until a thinfilm of the desired thickness, or a nanolaminate with the desiredstructure is grown.

In accordance with the preferred embodiments, the reactants of thepulses are selected to avoid etch damage to the workpiece surfaces.Example 8 below gives one embodiment in which the reactants do notsignificantly etch the surfaces.

More preferably, the reactants include species that are harmful to thesubstrate. However, a getter phase during each ALD cycle scavengesharmful species, thereby protecting sensitive surfaces while stillenabling employment of advantageous volatile reactants that areconducive to self-saturation in each phase. Examples 3, and 5-7, forinstance, disclose deposition processes that include a scavenging orgettering phase during each cycle. In the case of metal thin filmdeposition (Example 3), at least two different source chemicals arealternately employed, one of which getters halides from the otherchemical. In the case of metal nitride thin film deposition (Examples5-7), at least three different source chemicals are alternativelyemployed: a first reactant that forms no more than about one monolayerterminated with halogen ligands and including a species desired in thelayer being deposited; a getter for scavenging halides from themonolayer; and a second reactant that contains another species desiredin the layer being deposited, particularly nitrogen.

FIG. 8 illustrates generally a three-phase cycle for depositing binarymaterials. The skilled artisan will readily appreciate, however, thatthe principles disclosed here can be readily applied to depositingternary or more complex materials by ALD.

The semiconductor workpiece that includes sensitive surfaces is loadedinto a semiconductor processing reactor. An exemplary reactor, designedspecifically to enhance ALD processes, is commercially available fromASM Microchemistry of Finland under the tradename Pulsar 2000™.

If necessary, the exposed surfaces of the workpiece (e.g., the trenchand via sidewall surfaces and the metal floor shown in FIG. 6) areterminated to react with the first phase of the ALD process. The firstphases of the preferred embodiments are reactive, for example, withhydroxyl (OH) or ammonia (NH₃) termination. In the examples discussedbelow, silicon oxide and silicon nitride surfaces of the dual damascenestructure do not require a separate termination. Certain metal surfaces,such as at the bottom of the via 61 (FIG. 9A), can be terminated, forexample, with ammonia treatment.

After initial surface termination, if necessary, a first reactant pulseis then supplied 102 to the workpiece. In accordance with the preferredembodiments, the first reactant pulse comprises a carrier gas flow and avolatile halide species that is reactive with the workpiece surfaces ofinterest and further includes a species that is to form part of thedeposited layer. Accordingly, a halogen-containing species adsorbs uponthe workpiece surfaces. In the illustrated embodiments, the firstreactant is a metal halide, and the thin film being formed comprises ametallic material, preferably metal nitride. The first reactant pulseself-saturates the workpiece surfaces such that any excess constituentsof the first reactant pulse do not further react with the monolayerformed by this process. Self-saturation results due to halide tailsterminating the monolayer, protecting the layer from further reaction.

The first reactant pulse is preferably supplied in gaseous form, and isaccordingly referred to as a halide source gas. In some cases, thereactive species can have a melting point above the process temperature(e.g., CuCl melts at 430° C. while the process is conducted at about350° C.). Nevertheless, the halide source gas is considered “volatile,”for purposes of the present description, if the species exhibitssufficient vapor pressure under the process conditions to transport thespecies to the workpiece in sufficient concentration to saturate exposedsurfaces.

The first reactant is then removed 104 from the reaction space.Preferably, step 104 merely entails stopping the flow of the firstchemistry while continuing to flow a carrier gas for a sufficient timeto diffuse or purge excess reactants and reactant by-products from thereaction space, preferably with greater than about two reaction chambervolumes of the purge gas, more preferably with greater than about threechamber volumes. In the illustrated embodiment, the removal 102comprises continuing to flow purge gas for between about 0.1 seconds and20 seconds after stopping the flow of the first reactant pulse.Inter-pulse purging is described in co-pending U.S. patent applicationhaving Ser. No. 09/392,371, filed Sep. 8, 1999 and entitled IMPROVEDAPPARATUS AND METHOD FOR GROWTH OF A THIN FILM, the disclosure of whichis incorporated herein by reference. In other arrangements, the chambermay be completely evacuated between alternating chemistries. See, forexample, PCT publication number WO 96/17107, published Jun. 6, 1996,entitled METHOD AND APPARATUS FOR GROWING THIN FILMS, the disclosure ofwhich is incorporated herein by reference. Together, the adsorption 102and reactant removal 104 represent a first phase 105 in an ALD cycle.The first phase can also be referred to as a halide phase.

When the reactants of the first reactant pulse have been removed 104from the chamber, a getter pulse is supplied to the workpiece. Thegetter pulse scavenges or removes 106 (e.g., by ligand-exchange,sublimation or reduction) the ligand termination of the adsorbed complexmonolayer formed in step 102. A getter species, preferably along with acarrier flow, saturates the workpiece surfaces to ensure removal ofhalide tails prior to further pulses. Temperature and pressureconditions are preferably arranged to avoid diffusion of the getterthrough the monolayer to underlying materials.

As will be better understood from the more detailed discussion below,reaction between the halide tails on the adsorbed monolayer and thegetter species is thermodynamically favored. More particularly, reactionbetween the getter and the halide-terminated monolayer is generallycharacterized by a negative Gibb's free energy. Halide species thus bindto the getter species (or to a reaction by-product thereof, in the caseof scavenging by ligand-exchange) more readily than to the remainder ofthe adsorbed complex formed in the first phase 105. Similarly, thegetter may bind free halides in the reaction space.

The getter-halide complex (desirably also volatile) is then also removed108 from the reaction space, preferably by a purge gas pulse. Theremoval can be as described for step 104. Together, the scavenger pulse106 and removal 108 represent a second phase 109 of the illustrated ALDprocess, which can also be referred to as a scavenger or getter phase.

The first two phases are sufficient for the formation of metal films,such as a metal film layer in a nanolaminate structure. However, for theformation of binary metal layers, such as metal nitride layers, oneadditional phase is preferably employed. In other arrangements, thegetter can leave a component in place of the halide. For example, atriethyl boron getter can leave carbon when scavenging fluorine from atungsten complex.

In the illustrated embodiment, a second reactant pulse is then supplied110 to the workpiece. The second chemistry desirably reacts with oradsorbs upon the monolayer left by the getter phase 109. The getterphase is particularly useful when the second reactant comprises ahydrogen-bearing compound, such as tends to form hydrogen halides. Inthe illustrated embodiments, this second reactant pulse 110 comprisessupplying a carrier gas with a hydrogen-bearing nitrogen (e.g., NH₃)source gas to the workpiece. Nitrogen or nitrogen-containing speciesfrom the second reactant preferably reacts with the previously adsorbedmonolayer to leave a nitrogen compound. In particular, where the firstreactant comprises a metal halide, the second reactant leaves no morethan about a monolayer of metal nitride. The second reactant pulse 10also leaves a surface termination that operates to limit the depositionin a saturative reaction phase. Nitrogen and NH_(x) tails terminating ametal nitride monolayer are non-reactive with NH₃ of the second reactantpulse.

After a time period sufficient to completely saturate and react themonolayer with the second reactant pulse 110, the second reactant isremoved 112 from the workpiece. As with the removal 104 of the firstreactant and removal 108 of the getter species, this step 112 preferablycomprises stopping the flow of the second chemistry and continuing toflow carrier gas for a time period sufficient for excess reactants andreaction by-products from the second reactant pulse to diffuse out ofand be purged from the reaction space. Together, the second reactantpulse 110 and removal 112 represent a third phase 113 in the illustratedprocess, and can also be considered a nitrogen or hydrogen phase, sincenitrogen reacts with and forms a part of the growing film while hydrogenis released in the reaction.

In the illustrated embodiment, where three phases are alternated, oncethe excess reactants and by-products of the second chemistry have beenremoved from the reaction space, the first phase of the ALD process isrepeated. Accordingly, again supplying 102 the first reactant pulse tothe workpiece forms another self-terminating monolayer.

The three phases 105, 109, 113 thus together represent one cycle 115,which is repeated to form metal nitride monolayers in an ALD process.The first reactant pulse 102 generally reacts with the termination leftby the second reactant pulse 110 in the previous cycle. This cycle 115is repeated a sufficient number of times to produce a film of athickness sufficient to perform its desired function.

Though illustrated in FIG. 8 with only first and second reactants, alongwith an intermediate getter phase, it will be understood that, in otherarrangements, additional chemistries can also be included in each cycle.For example, if necessary, the cycle 115 can be extended to include adistinct surface preparation. Moreover, a second getter phase can beconducted in each cycle after the nitrogen phase 112. The cycle 115 thencontinues through steps 102 to 112. Furthermore, though illustrated withan initial metal phase and subsequent nitrogen phase in the examplesbelow, it will be understood that the cycle can begin with the nitrogenphase, depending upon the exposed substrate surfaces and phasechemistries.

In the production of nanolaminates, after the first monolayer of metal,metal carbide or metal nitride is deposited, the starting materials,pulsing parameters and cycle are preferably changed such that the phaseof the next monolayer is different and a phase interface is formedbetween any two film layers. For example, alternating a two phase andthree phase cycle would produce a nanolaminate structure withalternating metal and metal nitride layers. In another example, themetal source chemical is alternated in each repetition of the threephase cycle, producing alternating layers of metal nitrides.

In the illustrated metal nitride embodiments (Examples 5-7), the firstreactant comprises a metal halide, supplying metal to the growing layer(e.g., WF₆ or TiCl₄); the getter comprises triethyl boron (TEB); and thesecond reactant comprise ammonia (NH₃), contributing nitrogen to thegrowing layer.

The examples presented below demonstrate the benefit of using ahalogen-getter for the thin film deposition. Examples 1, 2 and 4illustrate with cases where corrosion of copper metal surface wasobserved and the other examples illustrate cases where the corrosion waseliminated in accordance with preferred embodiments. The extent ofcorrosion was not quantified. Corrosion was either present ornonexistent, as determined by optical and SEM imaging. In practice, thetolerance for corrosion will depend upon the application.

Source Materials

In general, the source materials, (e.g., metal source materials, halogengetters and nitrogen source materials), are preferably selected toprovide sufficient vapor pressure, sufficient thermal stability atsubstrate temperature and sufficient reactivity of the compounds foreffecting deposition by ALD. “Sufficient vapor pressure” supplies enoughsource chemical molecules in the gas phase to the substrate surface toenable self-saturated reactions at the surface at the desired rate.“Sufficient thermal stability” means that the source chemical itselfdoes not form growth-disturbing condensable phases on the surface orleave harmful level of impurities on the substrate surface throughthermal decomposition. One aim is to avoid uncontrolled condensation ofmolecules on the substrate. “Sufficient reactivity” results inself-saturation in pulses short enough to allow for a commerciallyacceptable throughput time. Further selection criteria include theavailability of the chemical at high purity and the ease of handling ofthe chemical.

The thin film transition metal nitride layers are preferably preparedfrom metal source materials and more preferably from the volatile orgaseous compounds of transition metals of groups 3, 4, 5, 6, 7, 8, 9,10, 11 and/or 12 of the periodic table of the elements. Elemental metalthin film layers are also preferably made from these compounds or fromstarting materials comprising Cu, Ru, Pt, Pd, Ag, Au and/or Ir. Morepreferably, metal and metal nitride source materials comprise transitionmetal halides.

1. Halide Source Materials

The first reactant preferably includes a species corrosive to surfacesof the workpiece exposed during the deposition, particularly whencombined with the second reactant. In the illustrated embodiment, thecorrosive species of the first reactant is advantageous in that itprovides a volatile source gas for delivering a desired depositingspecies. Moreover, the corrosive species facilitates self-limiteddeposition by forming a part of the ligand that inhibits further growthduring the first pulse.

Particularly, the first reactants of the preferred embodiments comprisehalides, and more preferably metal halides. As previously noted, metalhalides are volatile and therefore excellent vehicles for delivery ofmetal to the workpiece. Moreover, halogen tails terminate the surface ofthe chemisorbed monolayer, inhibiting further reaction. The surfaces arethus self-saturated to promote uniform film growth.

In the illustrated embodiments (see Examples 3 and 5-7 below), each ofthe halide source materials comprise a metal halide that tends to induceetching or corrosion during ALD reactions. Examples 1, 2 and 4, forinstance, each indicate corrosion of copper from exposure to ALDprocesses that include TiCl₄ or WF₆ pulses.

As shown by Example 8, however, TaF₅ does not etch copper during thetantalum nitride deposition. Thermodynamic calculations (see FIG. 5)support the experimental results and predict also that hafnium bromideand niobium fluoride do not corrode copper when depositing metal nitride(see FIG. 11). Low valence metal halides have less halogen atoms todonate and can be expected to corrode sensitive surfaces less than highvalence metal halides. Metal halide source chemical can be transportedover a reducing agent before the substrate space in order to lower thevalence or oxidation state of the metal in metal halide, thus reducingthe halide content of the metal halide and decreasing the corrosionprobability of substrate surfaces. The method of using a solid or liquidreducing agent before the substrate space is described in our pendingFinnish patent application FI 19992235. Metal sources such as TaF₅,hafnium bromide and niobium fluoride, therefore, are not considered tobe corrosive in the ALD processes at issue. Accordingly, such metalsource materials can be employed without the gettering method disclosedbelow.

The gettering method has been successfully employed with transitionmetal halides, especially with halides of elements selected from groupsIV (Ti, Zr and Hf), V (V, Nb and Ta) and VI (Cr, Mo and W) in theperiodic table of elements. The nomenclature of the groups is accordingto the system recommended by the IUPAC. Fluorides, chlorides, bromidesand iodides of transition metals can be used, depending on the specificmetal. Some metal-halogen compounds, for example ZrF₄, are not volatileenough for ALD processes.

2. Gettering or Scavenging Agents

2.1 Boron Compounds

In the examples, the gettering agent triethyl boron (TEB) was employedto protect copper surfaces against corrosion. Of the possible reactionproducts, the following ones are beneficial for the gettering effect:

-   -   Boron halides, formed by the reaction of halogen (e.g., from a        metal halide, hydrogen halide or ammonium halide) with the        center boron atom of the TEB molecule;    -   Ethyl halides, formed by the reaction of halogen (e.g., from a        metal halide, hydrogen halide or ammonium halide) with an ethyl        group of the TEB molecule; or    -   Ethane, formed by the reaction of hydrogen (e.g., from a        hydrogen halide molecule) and an ethyl group of the TEB        molecule.

It will be understood by those skilled in the art that the getteringeffect presented herein is not limited to TEB. One class of boroncompounds is boranes (B_(x)H_(y)).

Volatile boron compounds having at least one boron-carbon bond are morepreferred for certain metals, and hydrocarbon groups bound to boron aremore preferred. Very long or bulky groups bonded to boron may shield thecenter atom of the molecule so that the favored reactions will take toomuch time or may require unacceptable process conditions, such as toohigh substrate temperatures. Accordingly, a getter compound ispreferably selected from volatile boron compounds that have at least oneboron-carbon bond.

2.2 Silicon Compounds

Silicon compounds with, e.g., alkyl groups bound to silicon can be usedfor gettering halogens or hydrogen halides, as shown in reactionequations R1 and R2. It is assumed that each reaction with a hydrogenhalide molecule consumes one silicon-carbon bond. Accordingly, thegetter compound can be selected from volatile silicon compounds thathave at least one silicon-carbon bond.(CH₃CH₂)₄Si(g)+4HCl(g)→SiCl₄(g)+4CH₃CH₃(g)  [R1](CH₃)₂SiH₂(g)+2HCl(g)→SiH₂Cl₂(g)+2CH₄(g)  [R2]

2.3 Germanium and Tin Compounds

Germanium compounds with alkyl groups bound to germanium, as well asalkyl tin compounds, are within the bounds of possibility when getteringhalogens or hydrogen halides is needed. Accordingly, the getter compoundcan be selected from volatile germanium and tin compounds that have atleast one metal-carbon bond.

2.4 Aluminum, Zallium and Indium Compounds

In case of alkyl aluminum, gallium or indium compounds, the reactionsshow some harmful complexity. As an example, trimethylaluminum (TMA)decomposes in the presence of metal halides, leaving carbon on thesurfaces. Use of these compounds for gettering halogens or hydrogenhalides requires careful setup of ALD process parameters. However, inless preferred arrangements, the getter compound can be selected fromvolatile aluminum, gallium or indium compounds that have at least onemetal-carbon bond.

2.5 Carbon Compounds

In case of carbon compounds, it is possible to find a binding place forhydrogen halides when there exists double or triple bonded carbon in themolecule (R3 and R4). Calculating thermodynamical favorability for thereactions is difficult because surface chemistry differs from the gasphase chemistry e.g. due, for example, to the absorption and desorptionenergies. For getter compounds selected from volatile carbon compounds,the compounds preferably have at least one double or triple bond betweencarbon atoms.H₂C═CH₂(g)+HCl(g)→H₃C—CH₂Cl(g)  [R3] HC≡CH(g)+HF(g)→H₂C═CHF(g)  [R4]

2.6 Nitrogen Compounds

In case of nitrogen compounds, the problem is that usually nitrogenhalides are thermally unstable. Reactions between alkyl-nitrogen andhydrogen halide compounds forming any nitrogen halide are probably notfavorable. However, formation of alkyl chloride from alkyl amine istheoretically possible (R5). Free Gibb's energies (ΔG_(r)) werecalculated. Kinetic factors affecting the reaction speed have not beenresolved. Getter compounds selected from volatile amines preferably havenegative or near zero value of free Gibb's energy for the reactionbetween amine and the halogen-bearing species (e.g., hydrogen halide orammonium halide or free halogen), leading to the formation ofhalogenated carbon compound.CH₃NH₂(g)+HCl(g)→CH₃Cl(g)+NH₃(g) ΔG_(f)(400° C.)=−12 kJ  [R5]

Certain amines are stronger bases than ammonia (NH₃). Such amines canform a salt-like compound with an acidic hydrogen halide moleculewithout breaking it. The bonding enhances the removal of hydrogen halidefrom a copper metal surface before any corrosion occurs. Gettercompounds selected from volatile amines preferably form sufficientlystable salts with hydrogen halides or have negative or near zero valueof free Gibb's energy for the reaction between volatile amine andhydrogen halide that leads to the formation of volatileamine-hydrochloride salts.

2.7 Phosphor Compounds

Phosphor halides are quite stable and using organophosphor compounds forgettering halogens or hydrogen halides is possible. The formation ofmetal phosphides is a competing reaction and, depending on theapplication, phosphorus compounds may not be accepted. A getter compoundselected from phosphor compounds preferably has at least onephosphor-carbon bond.

2.8 Zinc Compounds

Alkyl zinc compounds are commercially available. Currently, zinc is notcompatible with state-of-the-art process flows for integrated circuits.Under circumstances where zinc exposure is acceptable, a getter compoundcan be selected from zinc compounds that have at least one zinc-carbonbond.

2.9 Iron and Lead Compounds

Organo-iron and organo-lead compounds form volatile metal halides. Agetter compound can be selected from iron or lead compounds that have atleast one metal-carbon bond.

2.10 Metallocene Compounds

A getter compound can be selected from volatile metallocenes, such asferrocene, dicyclopentadienyliron, or volatile derivatives ofmetallocenes, such as 1,1di(trimethylsilyl)ferrocene, said metals beingcapable of forming volatile metal halides.

2.11 Boron-silicon Compounds

A getter compound can also be selected from volatile boron-siliconcompounds that have at least one boron-silicon bond, such astris(trimethylsilyl)borane. Both silicon and boron are capable offorming volatile halides.

2.12 Metal Carbonyl Compounds

A getter compound can be selected from volatile metal carbonyls orvolatile derivatives of metal carbonyls, such as cyclohexadieneirontricarbony, where such metals are capable of forming volatile metalhalides.

2.13 General Reaction Equations for Organic Gettering Agents

A general reaction equation for the gettering of halogen with a volatileE(−CL₃)_(m)G_(n) compound is presented in R6. E is an element inperiodic table; L is a molecule bonded to carbon C; X is a halogen; G isan unspecified molecule or atom bonded to E; and m and n are integers,where the sum of m and n depends on the valence of E. There is achemical bond between E and C.E(—CL₃)_(m)G_(n)+HX→E(—X)(—CL₃)_(m−1)G_(n)+CL₃X  [R6]

A general reaction equation for the gettering of hydrogen halide with avolatile E(—CL₃)_(m)G_(n) compound is presented in R7. There is achemical bond between E and C. E is an element in periodic table; L is amolecule bonded to carbon C; X is a halogen; G is an unspecifiedmolecule or atom bonded to E; and m and n are integers, where the sum ofm and n depends on the valence of E. The reaction equations aresimplified. In reality there are additional reactions between thesurface and a chemisorbing E compound.E(—CL₃)_(m)G_(n)+HX→E(—X)(—CL₃)_(m−1)G_(n)+CL₃H  [R7]

The getter compounds E(—CL₃)_(m)G_(n) is selected from a chemicalcompound that can bind halogen or hydrogen halide or that can dissociatehydrogen halide or ammonium halide to form non-corroding volatilehalogen compounds.

2.14 Silane, Borane and Germanium Compounds

Regarding silanes (Si_(x)H_(y)) and boranes (B_(m)H_(n)) where x, y, mand n are positive integers, R8-R10 represent thermodynamicallyfavorable reactions that can bind hydrogen halides into less corrosivecompounds.SiH₄(g)+4HCl(g)→SiCl₄(g)+4H₂(g) ΔG_(f)(400° C.)=−269 kJ  [R8]BH₃(g)+3HCl(g)→BCl₃(g)+3H₂(g) ΔG_(f)(400° C.)=−193 kJ  [R9]B₂H₆(g)+6HCl(g)→2BCl₃(g)+6H₂(g) ΔG_(f)(400° C.)=−306kJ [R10]

Ammonium halides react with silanes and boranes (R11-R14), but they arealso capable of disturbing the growth of transition metal nitrides byforming silicon or boron nitride (R15-R18). The reactivity of ammoniumhalides is based on the well-known fact that they start to dissociateinto ammonia (NH₃) and hydrogen halide when heated.SiH₄(g)+4NH₄F→SiF₄(g)+4NH₃(g)+4H₂(g) ΔG_(f)(400° C.)=−711 kJ  [R11]SiH₄(g)+4NH₄Cl→SiCl₄(g)+4NH₃(g)+4H₂(g) ΔG_(f)(400° C.)=−303 kJ  [R12]BH₃(g)+3NH₄F→BF₃(g)+3NH₃(g)+3H₂(g) ΔG_(f)(400° C.)=−544 kJ  [R3]BH₃(g)+3NH₄Cl→BCl₃(g)+3NH₃(g)+3H₂(g) ΔG_(f)(400° C.)=−219 kJ  [R14]4SiH₄(g)+4NH₄F→SiF₄(g)+Si₃N₄+16H₂(g) ΔG_(f)(400° C.)=−1600 kJ  [R15]4SiH₄(g)+4NH₄Cl→SiCl₄(g)+Si₃N₄+16H₂(g) ΔG_(f)(400° C.)=−1193 kJ  [R16]4BH₃(g)+3NH₄F→BF₃(g)+3BN+12H₂(g) ΔG_(f)(400° C.)=−1549 kJ  [R17]4BH₃(g)+3NH₄Cl→BCl₃(g)+3BN+12H₂(g) ΔG_(f)(400° C.)=−1224 kJ  [R18]

When there are ammonium halide molecules NH₄F, NH₄C, NH₄Br, NH₄I) on thereaction chamber surface, it is beneficial to use as little silane orborane as possible to prevent the formation of non-volatile siliconnitride or boron nitride. When there are hydrogen halide molecules (HF,HCl, HBr, HI) on the reaction chamber surface, the dosage of silane orborane is adjusted so that acidic hydrogen halides form silicon halidesor boron halides, but there are practically no surplus silane or boranemolecules that could bind onto metal or metal nitride surface anddisturb the metal or metal nitride growth.

Germanes (Ge_(r)H_(t), where r and t are positive integers) can formvolatile germanium halides, especially with hydrogen halides.

Although there are just pure silicon-hydrogen, boron-hydrogen andgermanium-hydrogen compounds in the examples, a person skilled in theart will easily find in the literature that there exists series ofsimilar compounds useful as gettering agents. In silanes (Si_(x)H_(y)),boranes (B_(m)H_(n)) and germanes (Ge_(r)H_(t)), hydrogen atoms can bereplaced by halogen atoms one by one, for exampleSiH₄→SiH₃F→SiH₂F₂→SiHF₃. Mixed halogen compounds, such as SiH₂FCl, arealso possible. These compounds can serve as gettering agents as long asthere is at least one hydrogen atom bound to silicon, boron orgermanium.

As a general rule, a getter compound can be selected from silanes,boranes or germanes that have at least one hydrogen atom bound tosilicon, boron or germanium.

3. Source Materials for Second Reactant

The second reactant generally also includes a species corrosive tosurfaces of the workpiece exposed during the deposition, particularlywhen combined with the second reactant. In the illustrated embodiment,the corrosive species of the first reactant is advantageous in that itprovides a volatile source gas for delivering a desired depositingspecies.

In “pure” metal deposition by ALD, the second reactant is replaces withanother pulse of the first reactant. In Example 3, for instance, thefirst and second reactant pulses both comprise WF₆. Thus, only onereactant is alternated with the getter phase. Each WF₆ pulse canpotentially produce volatile halide compounds or free excited halidespecies that could corrode sensitive surfaces like copper, aluminum orsilicon oxide. Exposing a halide-terminated metal to ammonia, forexample, tends to produce hydrofluoric acid (HF) and ammonium fluoride(NH₄F).

For forming binary, ternary or more complex materials, a subsequentreactant preferably comprises a hydrogen-containing compound, and in theillustrated case of metal nitride deposition also provides nitrogen tothe metal nitride deposition process. The second reactant used as thenitrogen source material is preferably volatile or gaseous. Ammonia, forexample, is both volatile and highly reactive, promoting rapid reactionwith the chemisorbed species from the first reactant. Preferably, thesecond reactant is selected from the following group:

-   -   ammonia (NH₃);    -   salts of ammonia, preferably halide salt, in particular ammonium        fluoride or ammonium chloride;    -   hydrogen azide (HN₃) and the alkyl derivatives of the said        compound such as CH₃N₃;    -   Hydrazine (N₂H₄) and salts of hydrazine such as hydrazine        hydrochloride;    -   organic derivatives of hydrazine such as dimethyl hydrazine;    -   Nitrogen fluoride (NF₃);    -   primary, secondary and tertiary amines such as methylanine,        diethylamine and triethylamine;    -   nitrogen radicals such as NH₂*, NH** and N*** where “*”        designates a free electron capable of forming a bond; and    -   other excited species including nitrogen (N).

While the getter phase is of particular utility in combination withhydrogen-bearing reactants, it remains advantageous when employed priorto other reactants, such as the listed NF₃ and hydrogen-free nitrogenradicals.

Alternatively, this second reactant can provide carbon to form metalcarbides. For example, after a WF₆ pulse, it has been found that TEBdoes not merely getter halide tails, but rather leaves some carbon in aligand exchange reaction. Metal carbide serve as an excellent barriermaterial in place of, or in addition to, metal nitride within ananolaminate.

4. Selection Criteria Regarding Source Materials

Metal corrosion is expected if Gibb's energy (ΔG_(f)) is negative ornear zero for the reaction between

-   -   metal halide and metal;    -   hydrogen halide and metal; or    -   ammonium halide and metal,        where the metal represents a sensitive surface during a        reaction, and hydrogen halide and/or ammonium halide are formed        as by-products of surface reactions.

Silicon compound (e.g., silicon oxide or silicon nitride) corrosion isexpected on a surface if Gibb's free energy (ΔG_(f)) is negative or nearzero for the reaction between

-   -   hydrogen halide and silicon compound;    -   ammonium halide and silicon compound,        where the silicon compound represents a sensitive surface during        a reaction, and hydrogen halide and/or ammonium halide are        formed as by-products of surface reactions.

If theoretical calculations suggest that corrosion is possible, it isrecommended to add a getter to the process. The getter molecules combinewith corrosive molecules and prevent the corrosion of sensitivesurfaces.

The selection of the getter compound can be based on molecularsimulations. An exemplary simulation program is HyperChem release 4.5,commercially available from Hypercube Inc., Florida, USA. Said programhelps to visualize the physical appearance and electrostatic potentialgeometry of getter molecule candidates and to estimate whether or notmolecules, such as triethyl boron, have accessible areas for reactingwith corrosive molecules. Molecules with structures that are physicallyor electrostatically shielded from reaction with the potentially harmfulchemical make poor getters, as they increase the reaction times and thethroughput of a reactor will suffer. Simulation of reactions betweenmolecules and surfaces requires more complex software. Cerius²,commercially available from Molecular Simulation Inc. (MSI), USA, is anexample of a program capable of predicting the outcome of chemicalreactions.

The Chemistry

to further illustrate the chemistry in the transition metal nitride thinfilm growth, a plurality of examples are provided herein. Generally, aconformal and uniformly thick metal nitride is desired. ALD permitsmetal monolayers to be reacted with nitrogen in alternating pulses.

In the first scheme, titanium tetrachloride (TiCl₄) is taken as anexample of a metal source material and ammonia (NH₃) is an example of anitrogen-containing compound. The substrate is a silicon wafer having anative oxide on the surface. TiCl₄ reacts with the OH-containing surfacesites of the substrate.—OH(ads)+TiCl₄(g)→—O—TiCl₃(ads)+HCl(g)  [R19]

A reducing agent R is used to reduce TiCl₃ to TiCl₂.

 —O—TiCl₃(ads)+R(g)→—O—TiCl₂(ads)+RCl(g)  [R20]

possible reaction mechanisms between the nitrogen-containing compound,in this example NH₃, are numerous and complex. For example:—O—TiCl₃(ads)+NH₃(g)→—O—Ti(—Cl)₂—NH₂(ads)+HCl(g)  [R21]—O—Ti(—Cl)₂—NH₂(ads)→—O—Ti(—Cl)═NH(ads)+HCl(g)  [R22]—O—Ti(—Cl)₂—NH₂(ads)+NH₃(g)→—O—Ti(—Cl)(—NH₂)₂(ads)+HCl(g)  [R23]—O—Ti(—Cl)₂—NH₂(ads)→—O—Ti(NH)NH₂(ads)+HCl(g)  [R24]—O—Ti(—Cl)═NH(ads)→—O—Ti≡N(ads)+HCl(g)  [R25]—O—Ti(—Cl)═NH(ads)+NH₃(g)→—O—Ti(═NH)—NH₂(ads)+HCl(g)  [R26]—O—TiCl₃(ads)+NH₃(g)→—O—Ti(—Cl)═NH(ads)+2HCl(g)  [R27]—O—TiCl₃(ads)+NH₃(g)→—O—Ti≡N(ads)+3HCl(g)  [R28]

Reaction equations R21 through R28 refer to unreduced titanium.

The next TiCl₄ pulse will react with the active sites, such as byreactions 29 or 30:—O—Ti(—Cl)═NH(ads)+TiCl₄(g)→—Ti(—Cl)═N—TiCl₃(ads)+HCl(g)  [R29]—O—Ti(═NH)—NH₂(ads)+TiCl₄(g)→—O—Ti(═N—TiCl₃)—NH₂(ads)+HCl(g)  [R30]

Most favorable nitride surface sites for chemisorbing metal-containingconstituents especially metal halides, are sites with ═NH or —NH₂groups. The surface density of ═NH and —NH₂ groups may vary according tothe nitrogen source chemical used.

When aiming for lower resistivity, titanium with three bonds ispreferred because TiN has lower resistivity than nitrogen-rich titaniumnitride. In the final nitride crystal lattice, the bonding situation ismore complex than in the simplified scheme above because ions occupydifferent types of sites and the bonds can have ionic or covalentnature, as well as possible dangling bonds near crystal defects andgrain boundaries. Each pulsing cycle adds up to a molecular layer oftitanium or nitrogen containing species which form the nitride lattice.However, due to bulky ligands around absorbed metal atoms or a smallnumber of active surface sites, the growth rate can be less than onemolecular layer per cycle.

In the second scheme, tungsten hexafluoride (WF₆) is taken as an exampleof metal source material and ammonia (NH₃) is an example of a nitrogencompound rich in hydrogen. The substrate is a silicon wafer with asilicon dioxide (SiO₂) coating. There are surface sites with —OH groupson SiO₂. In a metal pulse, these sites react with WF₆ molecules (R19). Asubsequent ammonia pulse generates even more HF gas (R20). It must benoted that the presentation of W—N bonds is a simplified one. In realityW and N are forming a lattice and they share electrons with severalneighbor atoms.—OH(ads.)+WF₆(g)→O—WF₅(ads.)+HF(g)  [R31]—WF₅(ads.)+2NH₃(g)→—W(≡N)(═NH)(ads.)+5HF(g)  [R32]

Due to high HF production, a corrosive side reaction can occur on thesurface (R21). All the reaction products are highly volatile and theyleave the substrate. As a result SiO₂ is etched. As a generalization, itcan be said that incompatibility problems are possible when metalfluorides and hydrogen-rich nitrogen compounds contact silicon oxides.SiO₂(s)+4HF(g)→SiF₄(g)+2H₂O(g) ΔG_(f)(400° C.)=−43 kJ  [R33]

In the third scheme, there is a copper metal coating on the surface of asubstrate. Titanium tetrachloride (TiCl₄) is taken as an example of ametal chloride source chemical and ammonia (NH₃) is an example of anitrogen compound rich in hydrogen.Cu(s)+TiCl₄(g)→CuCl₄(s)+TiCl₄(s) ΔG_(f)(400° C.)=−11 kJ  [R34]Cu—OH(ads.)+TiCl₄(g)→Cu—O—TiCl₃(ads.)+HCl(g)—TiCl₃(ads.)+NH₃(g)→—Ti(—Cl)(—NH₂)(ads.)+HCl(G)

As discussed below, with respect to EXAMPLE 1, corrosion of the coppersurface is observed.2Cu(s)+2HCl(g)→2CuCl(s)+H₂(g) ΔG_(f)(400° C.)=−41 kJ  [R35]2Cu(s)+2NH₄Cl(s)→2CuCl(s)+H₂(g)+2NH₃(g) ΔG_(f)(400° C.)=−59 kJ  [R36]

EXAMPLES

In practicing the preferred embodiments, the conditions in the reactionspace are preferably arranged to minimize gas-phase reactions that canlead to the formation of condensed material. Reactions between specieschemisorbed on the surface and a gaseous reactant self-saturate.Reactions between by-products and a gaseous getter form volatilechemical compounds.

The deposition can be carried out at a wide range of pressureconditions, but it is preferred to operate the process at reducedpressure. The pressure in the reactor is preferably maintained betweenabout 0.01 mbar and 50 mbar, more preferably between about 0.1 mbar and10 mbar.

The substrate temperature is kept low enough to keep the bonds betweenthin film atoms below the surface intact and to prevent thermaldecomposition of the gaseous source chemicals. On the other hand, thesubstrate temperature is kept high enough to provide activation energybarrier for the surface reactions, to prevent the physisorption ofsource materials and minimize condensation of gaseous reactants in thereaction space. Depending on the reactants, the temperature of thesubstrate is typically 100° C.-700° C., preferably about 250° C.-400° C.

The source temperature is preferably set below the substratetemperature. This is based on the fact that if the partial pressure ofthe source chemical vapor exceeds the condensation limit at thesubstrate temperature, controlled layer-by-layer growth of the thin filmis compromised.

As the growth reactions are based on self-saturated surface reactions,there is no need for setting tight boundaries for pulse and purge times.The amount of time available for the pulsing cycle is limited mostly bythe economical factors, such as desired throughput of the product fromthe reactor. Very thin film layers can be formed by relatively fewpulsing cycles and in some cases this allows the use of low vaporpressure source materials with relatively long pulse times.

Example 1 The Deposition of TiN from TiC₄ and NH₃

A 200-mm silicon wafer coated with PVD copper was loaded into a Pulsar200™ ALD reactor, commercially available from ASM Microchemistry Oy ofEspoo, Finland. The substrate was heated to 400° C. in a flowingnitrogen atmosphere. The pressure of the reactor was adjusted to about 5mbar by the mass flow controller on the nitrogen line and a vacuum pump.Next, a TiN_(x) layer was grown by ALD from sequential pulses of TiC₄and NH₃ that were separated by inert nitrogen gas.

One deposition cycle consisted of the following steps:

-   -   TiC₄ pulse, for 0.05 s    -   N₂ purge for 1.0 s    -   NH₃ pulse for 0.75 s    -   N₂ purge for 1.0 s

This cycle was repeated 300 times to form about a 5-nm TiN_(x) film. Thegrowth rate of the TiN_(x) film was about 0.17 Å/cycle. Then the waferwas unloaded from the reaction for analysis. Four-point probe and EnergyDispersive Spectroscopy (EDS) measurements gave a resistivity of 150μΩcm.6TiCl₄(g)+8NH₃(g)→6TiN+24HCl(g)+N₂(g) ΔG_(f)(400° C.)=−19 kJ  [R37]

Equation R37 is a simplified presentation of the reaction. It is assumedthat there are reactive sites, such as —NH and ═NH, on the surface,which attract TiCl₄ molecules. After TiCl₄ pulse there are probably—TiCl₃ and ═TiCl₂ groups on the surface which can react with the NH₃molecules of the following pulse.

The theoretical result of equation R37 is a uniformly thick TiN_(x) filmover the copper surface. FIG. 2 shows, however, that there was pittingcorrosion on the copper film. Corrosion is initiated when HCl, which isformed as a by-product in the nitride growth (R37), reacts with copper.As HCl reacts easily with surplus NH₃, forming ammonium chloride(NH₄Cl), it is also possible that NH₄Cl acts as a gas-phase carrier forcopper chloride.

Example 2 Deposition of WN from WF₆ and NH₃

A 200-mm silicon wafer coated with PVD copper was loaded to a Pulsar2000 ALD reactor. The substrate was heated to 400° C. in a flowingnitrogen atmosphere. The pressure of the reactor was adjusted to about 5mbar by the mass flow controller on the nitrogen line and a vacuum pump.Next, a WN_(x) layer was grown by ALD from sequential pulses of WF₆ andNH₃ that were separated by inert nitrogen gas.

One deposition cycle consisted of the following steps:

-   -   WF₆ pulse for 0.25 s    -   N₂ purge for 1.0 s    -   NH₃ pulse for 0.75 s    -   N₂ purge for 1.0 s

This cycle was repeated 70 times to form about a 5-nm WN_(x) film. Thegrowth rate of the WN_(x) film was about 0.6 Å/cycle. Then the wafer wasunloaded from the reactor for analysis.

Etch damage to the copper film was visible even under an opticalmicroscope because of the nitride process. A lot of HF was evolves fromthe process (R38). HF may attack the copper surface (R39). Corrosion ofcopper was not expected because the vapor pressure of copper fluoride islow at the substrate temperature. HF, however, also readily reacts withsurplus NH₃ during the ammonia pulse, forming ammonium fluoride. Thus,NH₄F can act as a vapor phase carrier for CuF, resulting in corrosion.2WF₆(g)+4NH₃(g)→2WN+12HF(g)+N₂(g)  [R38]Cu+HF(g)→CuF+2H₂(g)  [R39]

Example 3 Deposition of WC_(x) with a Gettering Compound

A 200-mm silicon wafer coated with PVD copper was loaded into a Pulsar2000™ ALD reactor. The substrate was heated to about 400° C. in aflowing nitrogen atmosphere. The pressure of the reactor was adjusted toabout 5 mbar by the mass flow controller on the nitrogen line and avacuum pump. A thin film rich in tungsten metal was grown by ALD fromsequential pulses of WF₆ and triethyl boron (TEB), which were separatedby inert nitrogen gas.

One deposition cycle consisted of the following steps:

-   -   WF₆ pulse for 0.25 s    -   N₂ purge for 1.0 s    -   TEB pulse 0.05 for s    -   N₂ purge for 1.0 s

This cycle was repeated 70 times to form about a 5-nm W-rich tungstencarbide film. The growth rate of the thin film was about 0.6 Å/cycle.Then the wafer was unloaded from the reactor for analysis. No corrosionof copper was observed by Scanning Electron Microscopy (referred to asSEM hereinafter). The exact reaction mechanism between the monolayerleft by the WF₆ pulse and the TEB pulse is not known. It is assumed thatTEB acts as a halogen getter, forming boron fluoride and ethyl fluoridegases that leaves some carbon in the film.

Example 4 Deposition of W/TiN on Copper Metal

A 200-mm silicon wafer coated with PVD copper is loaded into a Pulsar2000™ ALD reactor. The substrate is heated to 350° C. in a flowingnitrogen atmosphere. The pressure of the reactor is adjusted to about 5mbar to 10 mbar by the mass flow controller on the nitrogen line and avacuum pump. Thin film rich in tungsten metal is grown by ALD fromsequential pulses of WF₆ and nido-pentaborane (B₅H₉), which areseparated by inert nitrogen gas:

One deposition cycle consists of the following steps:

-   -   WF₆ pulse for 1.0 s    -   N₂ purge for 1.0 s    -   B₅H₉ pulse for 3.0 s    -   N₂ purge for 1.0 s

The deposition cycle is repeated sufficient times to form about a 5-nmW-rich film. After that, a TiN_(x) layer is grown by ALD from sequentialpulses of TiCl₄ and NH₃, which are separated by inert nitrogen gas.

One deposition cycle consisted of the following steps:

-   -   TiCl₄ pulse for 0.05 s    -   N₂ purge for 1.0 s    -   NH₃ pulse for 0.75 s    -   N₂ purge for 1.0 s

The deposition cycle is repeated 200 times to form about a 5-rim TiN_(x)film over the tungsten film. Finally, the wafer is unloaded from thereactor for analyses. Corrosion of copper is observed by opticalmicroscope. Thus, 5 nm of W is not enough to protect the copper surfacefrom corrosive reactions during the TiN_(x) deposition by ALD.

Example 5 Deposition of WN with a Gettering Compound on Copper Metal

A 200-mm silicon wafer coated with PVD copper was loaded into a Pulsar2000™ ALD reactor. The substrate was heated to 400° C. in a flowingnitrogen atmosphere. The pressure of the reactor was adjusted to about 5mbar by the mass flow controller on the nitrogen line and a vacuum pump.Tungsten nitride thin film was grown by ALD from sequential pulses ofWF₆, TEB and NH₃ that were separated by inert nitrogen gas pulses.

One deposition cycle consisted of the following steps:

-   -   WF₆ pulse for 0.25 s    -   N₂ purge for 1.0 s    -   TEB pulse for 0.05 s    -   N₂ purge for 1.0 s    -   NH₃ pulse for 0.75 s    -   N₂ purge for 1.0 s

This cycle was repeated 70 times to form about a 5-nm W-rich film. Thegrowth rate of the thin film was about 0.6 Å/cycle. Then the wafer wasunloaded from the reactor for analysis.

No corrosion of copper was observed by SEM. The exact reaction mechanismbetween WF₆ and TEB is not known. It is assumed that TEB forms boronfluoride and ethyl fluoride gases, leaving negligible residue on thesurface.

Example 6 Deposition of WN/TiN Nanolaminate with a Gettering Compound

Two different types of 200-mm wafers were used for the experiment. Onewafer had a PVD copper coating while the other wafer had anElectrochemically Deposited (ECD) copper film. The copper-coated waferswere loaded into a Pulsar 2000™ ALD reactor, one by one. The substratewas heated to 400° C. in flowing nitrogen atmosphere. The pressure ofthe reactor was adjusted to about 5 mbar by the mass flow controller onthe nitrogen line and a vacuum pump.

First, a WN_(x) layer was grown by ALD from sequential pulses of WF₆,triethyl boron (TEB) and NH₃ that were separated by inert nitrogen gaspulses.

One deposition cycle consisted of the following steps:

-   -   WF₆ pulse for 0.25 s    -   N₂ purge for 1.0 s    -   TEB pulse for 0.05 s    -   N₂ purge for 0.3 s    -   NH₃ pulse for 0.75 s    -   N₂ purge for 1.0 s

TEB acts as a getter compound that can remove halogen from the surface.The deposition cycle was repeated 70 times to form about a 5-nm WN_(x)layer. The growth rate of WN_(x) was about 0.6 Å/cycle.

Next, a TiN_(x) layer was grown over the WN_(x) layer by ALD fromsequential pulses of TiCl₄ and NH₃ that were separated by inert nitrogengas pulses. One depsoition cycle consisted of the following steps:

-   -   TiCl₄ pulse for 0.05 s    -   N₂ purge for 1.0 s    -   NH₃ pulse for 0.75 s    -   N₂ purge for 1.0 s

This cycle was repeated 300 times to form about a 5-nm TiN_(x) film overthe WN_(x-1) film. The growth rate of the TiN_(x) film was about 0.17Å/cycle. Then the wafer was unloaded from the reactor for analysis.Four-point probe and Energy Dispersive Spectroscopy (EDS) measurementsgave a resistivity of about 140 μΩcm.

The same deposition program was used for both types of copper-coatedsilicon. FIGS. 3 and 4 show that there was no pitting or corrosion ofcopper during the deposition. Accordingly, 5 nm of WN_(x) was sufficientto protect underlying PVD or ECD copper from corrosion during theTiN_(x) deposition. Example 7

Deposition of TiN with a Gettering Compound on Copper Metal

A 200-mm silicon wafer coated with PVD copper was loaded into a Pulsar2000™ ALD reactor. The substrate was heated to 400° C. in a flowingnitrogen atmosphere. The pressure of the reactor was adjusted to about 5mbar by the mass flow controller on the nitrogen line and a vacuum pump.TiN layer was grown by ALD from sequential pulses of TiC₄, TEB and NH₃that were separated by inert nitrogen gas pulses.

One deposition cycle consisted of the following steps:

-   -   TiCl₄ pulse for 0.05 s    -   N₂ purge for 1.0 s    -   TEB pulse for 0.05 s    -   N₂ purge for 1.0 s    -   NH₃ pulse for 0.75 s    -   N₂ purge for 1.0 s

This cycle was repeated 300 times to form about a 5-nm TiN_(x) film. Thegrowth rate of the TiN_(x) film was about 0.17 Å/cycle. The wafer wasunloaded from the reactor for inspection. Optical microscope revealed nosigns of corrosion when used with the ×40 magnification. The exactnature of the surface reactions involved is not known. Without desiringto be limited by theory, it is believed that TiC₄ molecules preferablyattach to ═NH and —NH₂ groups on the surface. Some feasible reactionsliberating HCl are presented in (R28) and (R29). It is assumed that TEBscavenged liberated HCl.═NH(ads.)+TiCl₄(g)→═N—TiCl₃(ads.)+HCl(g)  [R40]—NH₂(ads.)+TiCl₄(g)→—N(—H)(—TiCl₃)(ads.)+HCl(g)  [R41]

Further process improvement is to add a TEB pulse following the NH₃pulse for absorbing the rest of the HCl molecules that can form in thesurface reactions. Some possible reactions liberating more HCl arepresented in equations R42 and R43.—TiCl₃(ads.)+NH₃(g)→—TiN(ads.)+3HCl(g)  [R42]═TiCl₂(ads.)+2NH₃(g)→═Ti(—NH₂)₂(ads.)+2HCl(g)  [R43]

Example 8 Deposition of Tantalum Nitride

A 50 mm×50 mm piece of copper-coated silicon wafer was loaded into anF-120™ ALD reactor, commercially available from ASM Microchemistry, Oyof Espoo, Finland. The substrate was heated to 400° C. in flowingnitrogen atmosphere. The pressure of the reactor was adjusted bynitrogen mass flow controller and a vacuum pump to about 5 mbar.Tantalum nitride layer was grown by ALD from sequential pulses of TaF₅and NH₃ that were separated by inert nitrogen gas.

One deposition cycle consisted of the following steps:

-   -   TaF₅ pulse for 0.2 s    -   N₂ purge for 1.0 s    -   NH₃ pulse for 1.0 s    -   N₂ purge for 2.0 s

This cycle was repeated 2000 times to form about a 16-nm Ta_(x)N_(y)film. The growth rate of the film was about 0.08 Å/cycle. The wafer wasunloaded from the reactor for inspection. Neither optical microscope norSEM showed any signs of copper corrosion.

Example 9 Deposition of a Nanolaminate Structure

A silicon substrate was loaded into an F-200™ ALD reactor, commerciallyavailable from ASM Microchemistry, Oy of Espoo, Finland. The reactorpressure was balanced to 5 mbar absolute by a vacuum pump and flowingnitrogen. The substrate was heated to 360° C. First, a titanium nitridefilm was grown no the substrate by repeating a pulsing sequence. Inertnitrogen gas carried titanium tetrachloride vapor into the reactionchamber. Surplus TiCl₄ and reaction by-products were purged away with N₂gas. After purging N₂ gas carried ammonia vapor to the reaction chamber.Surplus NH₃ and reaction by-products were purged away with N₂ gas:

-   -   TiCl₄ pulse for 0.05 s    -   N₂ purge for 1.0 s    -   NH₃ pulse for 0.75 s    -   N₂ purge for 1.0 s

A tungsten nitride thin film was grown on top of the titanium nitridefilm by repeating another pulsing sequence:

-   -   WF₆ pulse for 0.25 s    -   N₂ purge for 1.0 s    -   TEB pulse for 0.05 s    -   N₂ purge for 0.3 s    -   NH₃ pulse for 0.75 s    -   N₂ purge for 1.0 s

The processing was continued by depositing alternating thin film layersof titanium and tungsten nitride. Altogether 6 to 18 nitride thin filmlayers were deposited, depending on the sample. The total thickness ofthe ALD nanolaminate was approximately 70 nm. The film appeared as adark, light reflecting mirror. The color was slightly reddish, unlikeeither titanium or tungsten nitride. The film was analyzed bytransmission electron microscopy (TEM), energy dispersive spectroscopy(EDS) and four-point probe measurements. TEM pictures (FIG. 10) showed aclear nanolaminate structure with separate titanium and tungsten nitridethin film layers. According to EDS, there were titanium, tungsten andnitrogen molecules in the film. The amount of impurities was estimatedto be below 1 at.-%. The film was electrically conductive. Theresistivity was calculated by combining the thickness (EDS) andfour-point probe results. The resistivity of the non-optimized sampleswas approximately 400 μΩ-cm.

Example 10 Deposition of a Metal/Metal Nitride Nanolaminate Using TwoTransition Metal Sources

A nanolaminate was created with alternating thin film layers of metaland metal nitride, using the ALD processes described above. Twodifferent transition metal sources were used for the thin film layers.

-   -   Thin film layer 4: tantalum nitride.    -   Thin film layer 3: tungsten metal.    -   Thin film layer 2: tantalum nitride.    -   Thin film layer 1: tungsten metal.    -   Substrate.

Odd thin film layers (1, 3, 5 etc. . . . ) were deposited from atungsten source chemical and a reducing source chemical. Even thin filmlayers (2, 4, 6 etc. . . . ) were deposition from a tantalum sourcechemical, an optional reducing source chemical and a nitrogen sourcechemical. All source chemical pulses were separated from each other withan inert purge gas.

Example 11 Deposition of a Metal/Metal Nitride Nanolaminate Using OneTransition Metal

A nanolaminate was created with alternating thin film layers of metalnitride and metal. One transition metal source was used for the thinfilm layers.

-   -   Thin film layer 4: tungsten metal    -   Thin film layer 3: tungsten nitride.    -   Thin film layer 2: tungsten metal.    -   Thin film layer 1: tungsten nitride.    -   Substrate.

Odd thin film layers (1, 3, 5 etc. . . . ) were deposited from atungsten source chemical, an optional reducing source chemical and anitrogen source chemical. Even thin film layers (2, 4, 6 etc. . . . )were deposited from a tungsten source chemical and a reducing chemical.All source chemical pulses were separated from each other with an inertpurge gas.

Although the foregoing invention has been described in terms of certainpreferred embodiments, other embodiments will be apparent to those ofordinary skill in the art, in view of the disclosure herein.Accordingly, the present invention is not intended to be limited by therecitation of the preferred embodiments, but is instead to be defined byreference to the appended claims.

1. A method of forming a conductive nanolaminate structure on asubstrate within a reaction space comprising depositing at least threeadjacent thin film layers by atomic layer deposition (ALD) typeprocesses comprising sequential and alternating self-saturating surfacereactions, including at least one metal compound layer, wherein each ofthe at least three thin film layers is in a different phase fromdirectly adjacent ones of the at least three thin film layers.
 2. Themethod of claim 1, wherein the nanolaminate structure comprises at leastfour adjacent thin film layers deposited by the atomic layer deposition(ALD) type processes.
 3. The method of claim 1, wherein each of the atleast three adjacent thin film layers has a different composition fromdirectly adjacent ones of the at least three thin film layers.
 4. Themethod of claim 1, wherein the at least one metal compound thin filmlayer comprises a metal carbide.
 5. The method of claim 1, wherein theat least one metal compound thin film layer comprises a metal nitride.6. The method of claim 1, wherein at least one thin film layers of theat least three adjacent thin film layers comprises an elemental metal.7. The method of claim 1, wherein the nanolaminate structure is adiffusion barrier in an integrated circuit.
 8. The method of claim 1,wherein the nanolaminate is a conductive diffusion barrier.
 9. Themethod of claim 1, wherein the nanolaminate structure is formed on asubstrate susceptible to halide attack.
 10. The method of claim 9,wherein the ALD type process comprises providing alternating pulses ofreactants in a plurality of deposition cycles, each cycle comprising:supplying a first reactant to chemisorb no more than about one monolayerof a halide-terminated species over a surface of the substrate; removingexcess first reactant from the reaction space; and gettering halidesfrom the monolayer prior to repeating the cycle.
 11. The method of claim10, wherein each cycle further comprises supplying a hydrogen-bearingsecond reactant.
 12. The method of claim 11, wherein the hydrogenbearing second reactant comprises a source of nitrogen.
 13. The methodof claim 12, wherein the source of nitrogen comprises ammonia.
 14. Themethod of claim 12, wherein the first reactant comprises a metal halide.15. The method of claim 10, wherein the surface comprises metal.
 16. Themethod of claim 10, wherein gettering comprises reducing.
 17. A methodof forming a conductive nanolaminate structure on a substratesusceptible to halide attack within a reaction space by an atomic layerdeposition (ALD) process, the nanolaminate structure comprising at leasttwo adjacent thin film layers, including at least one metal compoundlayer, wherein each of the at least two adjacent thin film layers is ina different phase from directly adjacent ones of the at least twoadjacent thin film layers, and wherein the atomic layer depositionprocess comprises providing alternating pulses of reactants in aplurality of deposition cycles, each cycle comprising: supplying a firstreactant to chemisorb no more than about one monolayer of a halidespecies over a surface of the substrate, removing excess first reactantfrom the reaction space; and gettering halides from the monolayer priorto repeating the cycle, wherein the surface comprises copper.
 18. Themethod of claim 17, wherein the surface further comprises a form ofsilicon oxide.
 19. A method of forming a conductive nanolaminatestructure on a substrate susceptible to halide attack within a reactionspace by an atomic layer deposition (ALD) process, the nanolaminatestructure comprising at least two adjacent thin film layers, includingat least one metal compound layer, wherein each of the at least twoadjacent thin film layers is in a different phase from directly adjacentones of the at least two adjacent thin film layers, and wherein theatomic layer deposition process comprises providing alternating pulsesof reactants in a plurality of deposition cycles, each cycle comprising:supplying a first reactant to chemisorb no more than about one monolayerof a halide species over a surface of the substrate, removing excessfirst reactant from the reaction space; and gettering halides from themonolayer prior to repeating the cycle, wherein the surface is formed bya material less than 5 nm thick over copper.
 20. A method of forming aconductive nanolaminate structure on a substrate susceptible to halideattack within a reaction space by an atomic layer deposition (ALD)process, the nanolaminate structure comprising at least two adjacentthin film layers, including at least one metal compound layer, whereineach of the at least two adjacent thin film layers is in a differentphase from directly adjacent ones of the at least two adjacent thin filmlayers, and wherein the atomic layer deposition process comprisesproviding alternating pulses of reactants in a plurality of depositioncycles, each cycle comprising: supplying a first reactant to chemisorbno more than about one monolayer of a halide species over a surface ofthe substrate, removing excess first reactant from the reaction space;and gettering halides from the monolayer prior to repeating the cycle,wherein gettering comprises reducing by exposing the halide-terminatedspecies to a boron compound.
 21. The method of claim 20, wherein theboron compound comprises triethyl boron (TEB).